mirror of https://github.com/k3s-io/k3s
206 lines
7.0 KiB
Markdown
206 lines
7.0 KiB
Markdown
go-spew
|
|
=======
|
|
|
|
[]
|
|
(https://travis-ci.org/davecgh/go-spew) [![ISC License]
|
|
(http://img.shields.io/badge/license-ISC-blue.svg)](http://copyfree.org) [![Coverage Status]
|
|
(https://img.shields.io/coveralls/davecgh/go-spew.svg)]
|
|
(https://coveralls.io/r/davecgh/go-spew?branch=master)
|
|
|
|
|
|
Go-spew implements a deep pretty printer for Go data structures to aid in
|
|
debugging. A comprehensive suite of tests with 100% test coverage is provided
|
|
to ensure proper functionality. See `test_coverage.txt` for the gocov coverage
|
|
report. Go-spew is licensed under the liberal ISC license, so it may be used in
|
|
open source or commercial projects.
|
|
|
|
If you're interested in reading about how this package came to life and some
|
|
of the challenges involved in providing a deep pretty printer, there is a blog
|
|
post about it
|
|
[here](https://web.archive.org/web/20160304013555/https://blog.cyphertite.com/go-spew-a-journey-into-dumping-go-data-structures/).
|
|
|
|
## Documentation
|
|
|
|
[]
|
|
(http://godoc.org/github.com/davecgh/go-spew/spew)
|
|
|
|
Full `go doc` style documentation for the project can be viewed online without
|
|
installing this package by using the excellent GoDoc site here:
|
|
http://godoc.org/github.com/davecgh/go-spew/spew
|
|
|
|
You can also view the documentation locally once the package is installed with
|
|
the `godoc` tool by running `godoc -http=":6060"` and pointing your browser to
|
|
http://localhost:6060/pkg/github.com/davecgh/go-spew/spew
|
|
|
|
## Installation
|
|
|
|
```bash
|
|
$ go get -u github.com/davecgh/go-spew/spew
|
|
```
|
|
|
|
## Quick Start
|
|
|
|
Add this import line to the file you're working in:
|
|
|
|
```Go
|
|
import "github.com/davecgh/go-spew/spew"
|
|
```
|
|
|
|
To dump a variable with full newlines, indentation, type, and pointer
|
|
information use Dump, Fdump, or Sdump:
|
|
|
|
```Go
|
|
spew.Dump(myVar1, myVar2, ...)
|
|
spew.Fdump(someWriter, myVar1, myVar2, ...)
|
|
str := spew.Sdump(myVar1, myVar2, ...)
|
|
```
|
|
|
|
Alternatively, if you would prefer to use format strings with a compacted inline
|
|
printing style, use the convenience wrappers Printf, Fprintf, etc with %v (most
|
|
compact), %+v (adds pointer addresses), %#v (adds types), or %#+v (adds types
|
|
and pointer addresses):
|
|
|
|
```Go
|
|
spew.Printf("myVar1: %v -- myVar2: %+v", myVar1, myVar2)
|
|
spew.Printf("myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
|
|
spew.Fprintf(someWriter, "myVar1: %v -- myVar2: %+v", myVar1, myVar2)
|
|
spew.Fprintf(someWriter, "myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
|
|
```
|
|
|
|
## Debugging a Web Application Example
|
|
|
|
Here is an example of how you can use `spew.Sdump()` to help debug a web application. Please be sure to wrap your output using the `html.EscapeString()` function for safety reasons. You should also only use this debugging technique in a development environment, never in production.
|
|
|
|
```Go
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"html"
|
|
"net/http"
|
|
|
|
"github.com/davecgh/go-spew/spew"
|
|
)
|
|
|
|
func handler(w http.ResponseWriter, r *http.Request) {
|
|
w.Header().Set("Content-Type", "text/html")
|
|
fmt.Fprintf(w, "Hi there, %s!", r.URL.Path[1:])
|
|
fmt.Fprintf(w, "<!--\n" + html.EscapeString(spew.Sdump(w)) + "\n-->")
|
|
}
|
|
|
|
func main() {
|
|
http.HandleFunc("/", handler)
|
|
http.ListenAndServe(":8080", nil)
|
|
}
|
|
```
|
|
|
|
## Sample Dump Output
|
|
|
|
```
|
|
(main.Foo) {
|
|
unexportedField: (*main.Bar)(0xf84002e210)({
|
|
flag: (main.Flag) flagTwo,
|
|
data: (uintptr) <nil>
|
|
}),
|
|
ExportedField: (map[interface {}]interface {}) {
|
|
(string) "one": (bool) true
|
|
}
|
|
}
|
|
([]uint8) {
|
|
00000000 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 |............... |
|
|
00000010 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 |!"#$%&'()*+,-./0|
|
|
00000020 31 32 |12|
|
|
}
|
|
```
|
|
|
|
## Sample Formatter Output
|
|
|
|
Double pointer to a uint8:
|
|
```
|
|
%v: <**>5
|
|
%+v: <**>(0xf8400420d0->0xf8400420c8)5
|
|
%#v: (**uint8)5
|
|
%#+v: (**uint8)(0xf8400420d0->0xf8400420c8)5
|
|
```
|
|
|
|
Pointer to circular struct with a uint8 field and a pointer to itself:
|
|
```
|
|
%v: <*>{1 <*><shown>}
|
|
%+v: <*>(0xf84003e260){ui8:1 c:<*>(0xf84003e260)<shown>}
|
|
%#v: (*main.circular){ui8:(uint8)1 c:(*main.circular)<shown>}
|
|
%#+v: (*main.circular)(0xf84003e260){ui8:(uint8)1 c:(*main.circular)(0xf84003e260)<shown>}
|
|
```
|
|
|
|
## Configuration Options
|
|
|
|
Configuration of spew is handled by fields in the ConfigState type. For
|
|
convenience, all of the top-level functions use a global state available via the
|
|
spew.Config global.
|
|
|
|
It is also possible to create a ConfigState instance that provides methods
|
|
equivalent to the top-level functions. This allows concurrent configuration
|
|
options. See the ConfigState documentation for more details.
|
|
|
|
```
|
|
* Indent
|
|
String to use for each indentation level for Dump functions.
|
|
It is a single space by default. A popular alternative is "\t".
|
|
|
|
* MaxDepth
|
|
Maximum number of levels to descend into nested data structures.
|
|
There is no limit by default.
|
|
|
|
* DisableMethods
|
|
Disables invocation of error and Stringer interface methods.
|
|
Method invocation is enabled by default.
|
|
|
|
* DisablePointerMethods
|
|
Disables invocation of error and Stringer interface methods on types
|
|
which only accept pointer receivers from non-pointer variables. This option
|
|
relies on access to the unsafe package, so it will not have any effect when
|
|
running in environments without access to the unsafe package such as Google
|
|
App Engine or with the "safe" build tag specified.
|
|
Pointer method invocation is enabled by default.
|
|
|
|
* DisablePointerAddresses
|
|
DisablePointerAddresses specifies whether to disable the printing of
|
|
pointer addresses. This is useful when diffing data structures in tests.
|
|
|
|
* DisableCapacities
|
|
DisableCapacities specifies whether to disable the printing of capacities
|
|
for arrays, slices, maps and channels. This is useful when diffing data
|
|
structures in tests.
|
|
|
|
* ContinueOnMethod
|
|
Enables recursion into types after invoking error and Stringer interface
|
|
methods. Recursion after method invocation is disabled by default.
|
|
|
|
* SortKeys
|
|
Specifies map keys should be sorted before being printed. Use
|
|
this to have a more deterministic, diffable output. Note that
|
|
only native types (bool, int, uint, floats, uintptr and string)
|
|
and types which implement error or Stringer interfaces are supported,
|
|
with other types sorted according to the reflect.Value.String() output
|
|
which guarantees display stability. Natural map order is used by
|
|
default.
|
|
|
|
* SpewKeys
|
|
SpewKeys specifies that, as a last resort attempt, map keys should be
|
|
spewed to strings and sorted by those strings. This is only considered
|
|
if SortKeys is true.
|
|
|
|
```
|
|
|
|
## Unsafe Package Dependency
|
|
|
|
This package relies on the unsafe package to perform some of the more advanced
|
|
features, however it also supports a "limited" mode which allows it to work in
|
|
environments where the unsafe package is not available. By default, it will
|
|
operate in this mode on Google App Engine and when compiled with GopherJS. The
|
|
"safe" build tag may also be specified to force the package to build without
|
|
using the unsafe package.
|
|
|
|
## License
|
|
|
|
Go-spew is licensed under the [copyfree](http://copyfree.org) ISC License.
|